On Sun, 23 Jul 2017 12:15:03 -0700, Duster wrote:

Pileus clouds are cap-like clouds that can be used to identify thermal
wave. Good convection apparently acts like orographic barrier, wind
shear hits it, forced up and moisture condences. Climb is on windward
side of cumulus, from my limited experience. The Pileus often don't last
very long, though the lift may still be there.

https://www.youtube.com/watch?v=mGM7kJQr0RA

https://www.youtube.com/watch?v=3eHKYWMvmWE

I didn't know the name until now, but I remember some years ago coming
off the Channel car ferry at Calais and heading for Hungary. This took us
through Lille and across Belgium into Germany at Aachen. All the way
across Belgium there were really good-looking Cu with Pileus caps on the
northerly slopes of most of them with bright sun on the ground and a
decent northerly blow, so good, unstable, thermally lower atmosphere. I
remember thinking that this would have a been a great day to have taken
an early launch in southern England to cross the Channel and see how far
into France or Germany you could get.

The trick seems to be to leave the English coast high enough to get to
France with enough height move away from the coast and into the first
thermal region. Still, you may get lucky on the way. I remember reading
that Philip Wills was lucky enough to drift most of the way across in
what sounds like some sort of self-recycling lift bubble before leaving
as it decayed and finally landing at St.Omer, 30km from the coast, as the
day died.


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martin@ | Martin Gregorie
gregorie. | Essex, UK
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